1. Technical Field
This invention relates to apparatus for cleaning underwater structures and in particular to the removal of debris collecting on trash racks.
2. Background Art
Power generating systems, be they fossil-fueled, nuclear-based, or hydro-electric, are dependent on a non-interruptable source of water. In general, the water intake requirements for public utilities and private factories can amount to thousands of gallons per minute. Depending on the application, the demand for water may vary between the maximum intake possible to almost no water at all within a short period of time. Usually such intake water is drawn from some type of open reservoir, e.g., lakes, rivers or the ocean. Due to the high flow rates of the water drawn in for this purpose, water intake systems have long been plagued by problems of trash and marine life entrainment. As an initial filtration to eliminate trash, large gratings are often placed at the point where water first enters the system. The purpose of these initial filters or trash racks is to allow the free flow of water while at the same time intercepting the larger components of water-borne debris. Because such trash racks tend to become clogged with debris it is necessary to clean the surface of the racks in order to remove the debris and marine matter which impede the flow of water.
To alleviate the arduous task of periodically pulling the trash racks out of the water for maintenance, there has been a great deal of effort devoted to cleaning the racks while they are submerged. This in situ cleaning usually involves various juryrigged scrapers that are hauled across the trash racks from above. These scraping techniques tend to damage the racks' protective paint covering, hastening the need for a complete removal of the trash rack and re-painting. The need to repaint is especially critical where the racks are immersed in sea water.
Currently the trash rack cleaning involves a metal rake or comb which is hauled or pushed, with the help of a crane, over the trash rack structure. U.S. Pat. No. 3,755,864 issued to Sandler (1973) discloses a method of cleaning trash racks that uses rakes mounted on a circular track. The teeth of the rake as disclosed in the Sandler patent are continually swept along the longitudinal length of the rack to be cleaned. The problem with this method is that the mechanism necessary to drive the rakes in such a system is complex and difficult to move from one rack to another. Another currently-available method of cleaning trash racks involves hydraulic mechanisms that move a rake over the length of the trash rack. This method, too, involves the use of heavy expensive equipment that is difficult to move laterally from one rack to another.
What is needed is a relatively light and transportable cleaning apparatus that will not damage the surface of the underwater structure that is to be cleaned. It is the object of this invention to implement an easy-to-use and maneuverable cleaning system for underwater trash racks.